This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This trial is a multicenter, international, randomized, double blind placebo-controlled trial of the aldosterone antagonist, spironolactone, in 4500 adults with heart failure and left ventricular ejection fraction of at least 45%, recruited from over 150 clinical centers. The primary endpoint is a composite of cardiovascular mortality, aborted cardiac arrest or hospitalization for the management of heart failure. Secondary endpoints include all-cause mortality, new onset of diabetes mellitus, atrial fibrillation, and quality of life. The trial duration is 4.5 years, with 2.5 years for subject enrollment and an additional 2 years of follow-up, for an average subject follow-up of 3.25 years. Dynamic balancing by clinical center at the time of randomization will be used to ensure that the distribution of clinical centers are similar in the two treatment groups.